MAP: How much energy is the world using?

It may come as no surprise that large, energy-rich countries like the United States use the most energy, but how much per person? And which countries are using the least?

This map includes energy consumption data from the International Energy Agency and includes electricity, as well as fossil and gathered fuels. The numbers are from 2010 – the last year for which complete numbers are available.

For a larger view, click the map below, or click here.


WorldMap - Energy Consumption Per Capita 2010


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The Global Energy Mix and Policies

 On this page, you can find energy information about the world’s most populated countries: China, India, the United States, Indonesia, Brazil, Pakistan, Bangladesh, Nigeria, Russia, and Japan. For fossil fuel information about any country, see online tables here.

A nation’s sources of energy hinge on so many factors, from what’s naturally available to geography, political history, and relative wealth.

Even though energy demand is increasing rapidly across the globe, the International Energy Agency estimates a fifth of the world population lacks access to electricity, and a whopping 40 percent of people still use traditional biomass – like wood chips – for cooking. People who live without the energy infrastructure of electricity depend on portable petroleum fuels, manure and methane gas produced from manure, wood, grass, and agricultural wastes. Because these sources of energy are informal, it’s difficult to track and include them in statistics.

World electricity and energy demands are escalating. Countries are expanding energy investment to non-fossil sources like biofuels, wind, solar, and geothermal. At the same time, they are competing to secure access to coal, natural gas, and petroleum both at home and abroad.


Nowhere has rapid energy growth been more conspicuous than in the world’s most populated country, China. While most countries saw moderate energy growth in the same period, this Asian nation doubled energy use in less than a decade – see graph – and surpassed the United States in total energy use in 2009, according to International Energy Agency estimates. Until 2009, the United States lead the world in total energy consumption, though not per person consumption, for decades. For a list of the top 30 countries by total energy consumption see here.

Meanwhile, less than 42 percent of people in Africa had electricity at home in 2009. South Asians seemed better off than Africans that year, at 62 percent, but the real story is much more diverse. Nearly 100 percent of Chinese had access to electricity, while in Burma, only 13 percent had access. Worldwide almost 78 percent of people had access to electricity in 2009, according to the International Energy Agency.




CHINA (Pop. 1.3 billion)

Between 2008 and 2035, China may triple its electricity demand, adding power plant capacity equal to the current U.S. total, the International Energy Agency projects in one scenario of the 2010 World Energy Outlook.

China is the world’s most populated country and also the world’s largest energy consumer. China gets most of its energy from coal, 71 percent in 2008. China is also the world’s biggest coal producer but only third, behind the United States and Russia, in coal reserves.

In 2008, China generated another 19 percent of its energy from oil, which it imported from all over the world, more than half came collectively from Saudi Arabia, Angola, Iran, Oman, Russia, and Sudan. China used to export its oil, but by 2009 automobile investment was expanded by so much, the country became the second largest oil importer (United States is first).

China is in hot pursuit of securing as much oil as possible, as the nation’s reliance on imported oil is growing far more rapidly than its oil production. Several powerful, national oil companies provide the domestic oil, both from on and off-shore sources. Furthermore, China has purchased oil assets in the Middle East, Canada, and Latin America, and it also conducts oil-for-loan exchanges with other countries, $90 billion worth since 2009, according to the U.S. Energy Information Administration.

Only a small proportion of China’s energy comes natural gas, produced domestically and imported in liquified form, but that may change as prices lower and liquified natural gas terminals are constructed.

China is the world’s biggest user of hydroelectric power, which made up 6 percent of energy and 16 percent of electricity in 2009. The country’s Three Gorges Dam, the world’s largest hydroelectric project, is expected to begin operating in 2012. Nuclear power accounts for only 1 percent of total consumption. However, China’s government predicts it will have seven times its current nuclear capacity by 2020.

A homemade oven. West Bengal, India, 2009.

Detailed data on energy in China can be found here.







INDIA (1.2 billion)

India is the world’s largest democracy. Though India’s population is close to that of China’s, it is only the world’s fifth largest energy user, behind the United States, China, Russia, and Japan.

Like China, India’s electricity comes mostly from coal. However, India doesn’t have enough electricity for everyone, and only 65 percent of the population has access to electricity.

Instead, many Indian use fuels at home for lighting and cooking. A 2004-2005 survey by the government found more than 40 percent of rural Indians used kerosene instead of electricity for home lighting. The same survey showed that for cooking, 74 percent of Indians used firewood and wood chips, 8.6 percent used liquified petroleum gas, 9 percent used dung cakes, and 1.3 percent used kerosene.

India produces oil domestically, but like China, the rate of India’s increasing oil consumption far outstrips its production. India therefore has to import oil; in 2009 its most significant sources were Saudi Arabia, Iran, Kuwait, Iraq, the United Arab Emirates, Nigeria, Angola, and Venezuela, in descending order.

India doesn’t have the electricity capacity to serve its population but aims to add many thousands of megawatts in the near future.

Like China, India has nuclear power, with 14 nuclear plants in operation and another 10 in planning, the reactors purchased from France and Russia.


UNITED STATES (300 million)

Until China recently outpaced it, the United States was the biggest energy consumer in the world, though per capita use isn’t the highest but in the same range as several developed countries worldwide and less than the per capita use in Canada. The United States relies on petroleum, coal, and natural gas, as well as a small part nuclear, hydroelectric, and various non-fossil sources. The Unites States has significant oil, coal, and natural gas reserves, as well as the potential for significant investment in solar, off and on-shore wind, and biofuels.

The mix of fuels that provide electricity varies widely from region to region. Find a map of fuel mix by U.S. region from the Edison Electric Insitute here.

For more U.S. information:

-Fossil fuel use in the United States, go here.
-U.S. greenhouse gas emissions and energy here.
-U.S. sources of energy, see here.


INDONESIA (250 million)

Indonesia is an archipelago of more than 17,000 islands — 6,000 are inhabited — and it is home to 76 active volcanoes and a significant undeveloped geothermal capacity, estimated at 28 gigawatts, about as much total electricity capacity as Indonesia had in 2008.

Indonesia’s energy demand is growing rapidly, split between coal, natural gas, and petroleum sources. Traditional sources of energy like wood and agricultural waste continue to be used, particularly in rural areas and remote islands, and the International Energy Administration estimates these fuels provide about a quarter of the country’s energy.

Indonesia exports coal and natural gas. In the past, the country also exported more oil than it used, but as of 2004 that balance changed. By 2009, the country suspended its membership in the Organization of Petroleum Exporting Countries (OPEC) because it was using so much of its own oil.


BRAZIL (200 million)

Tropical Brazil is the largest country in South America both in area and population, and it is the third largest user of energy in the Americas, after the United States and Canada.

Made from sugar cane, Brazil’s ethanol production is the world’s second largest, after the United States, which makes ethanol from corn.

Brazil produces almost as much petroleum as Venezuela and produces slightly more fuel than it consumes.

While Brazil depends on oil for other energy applications like transportation, the country gets an astounding 84 percent of electricity from hydroelectric dams. Brazil also has two nuclear power plants.

PAKISTAN (190 million)

Pakistan has limited access to electricity and energy sources, and its rural population still relies on gathered fuels like wood for heating and cooking.

In 2009 around 60 percent of the population had access to electricity, far better than its neighbor Afghanistan, at just 15 percent. Nonetheless, even with access, most of the population can’t rely on electricity unless they are wealthy enough to own generators. Pakistan suffers from lengthy blackouts, even in its cities, in part because of poor transmission infrastructure and widespread electricity theft. The situation is also aggravated by lack of capacity planning, insufficient fuel, and irregularities in water supply for hydroelectric.

In 2010, angry citizens protested violently after lengthy blackouts — as long as 18 hours according to Reuters — plagued the country. That summer, Pakistan has nowhere near enough electricity for its peak needs, which were roughly 25 percent more than its total production capacity. The widespread blackouts crippled the country’s textile industry, its biggest source of exports, and some reports suggest that hundreds of factories were shuttered as a result of sporadic power.

Meanwhile, several proposals for gas pipelines through Pakistan have yet to get solidified, including one from Iran to Afghanistan (which is opposed by the United States).


BANGLADESH (160 million)

Like nearby Pakistan and India, with which it shares cultural and political histories, Bangladesh also suffers from electricity shortages. Only 41 percent of Bangladeshis had access to electricity in 2009, according to the International Energy Administration.

Most of the electricity in this delta nation is generated from natural gas, with smaller amounts each from oil, coal, and hydroelectric sources. More than 30 percent of the country’s energy comes from biomass, agricultural wastes, and other combustible, renewable materials.

In 2011, Bangladesh signed a contract with oil company ConocoPhillips, allowing off-shore drilling for natural gas, despite internal protests that insisted Bangladesh should keep more of the gas for its own. The agreement gives 20 percent to Bangladesh.


NIGERIA (160 million)

Nigeria is Africa’s most populous country, and it is world famous for its oil, most of which is exported for sale by huge foreign oil companies like Royal Dutch Shell, ExxonMobil, Chevron, ConocoPhillips, Petrobras, and Statoil. Roughly 65 percent of government revenue comes from the oil sector, and around 40 percent its oil exports are sent to the United States. Nigeria also holds the largest natural gas reserves in Africa.

Extensive oil development has wreaked havoc on Nigeria’s ecology. Oil spills have polluted Nigeria’s water, affecting both fishing and agriculture. Much of Nigeria’s natural gas is flared rather than being collected and sold for fuel. Flaring involves burning off naturally-occurring gases during petroleum drilling and refining, resulting in  environmental degradation, greenhouse gas emissions and loss of revenue.

Even though Nigeria is fossil fuel-rich, only 47 percent of the population have access to electricity, and less than a fifth of energy in that country came from petroleum and natural gas in 2007, reflecting the widespread use of more traditional fuels like wood. Nigeria only used 13 percent of petroleum it produced in 2009.


RUSSIA (140 million)

Russia has significant wealth in fossil fuels, including the largest natural gas reserves and the second largest coal reserves, after the United States. In 2009, Russia produced more oil even than Saudi Arabia, mostly from Western Siberia. In 2009, Russia exported far more oil than it used, and 81 percent of its exports went to Europe, notably the Netherlands and Germany.

Russia is also the third largest consumer of energy in the world.

The country has a well-developed pipeline system to transport oil from remote regions, a system which is almost entirely controlled by a single state-run company, Transneft.

Like Nigeria, Russia flares gas in the process of drilling and refining oil, and in 2008 Russia flared more gas than any other country in the world, 1,432 Bcf of natural gas, more than double Nigeria’s output and equivalent to the annual greenhouse gas emissions for 1.4 million passenger cars, according the calculator on the U.S. Environmental Protection Agency website and data from the U.S. Energy Information Administration.

Russia operates 31 nuclear reactors, half of which employ a similar design to the ill-fated Chernobyl plant in the Ukraine.


JAPAN (130 million)

Japan doesn’t have significant fossil fuel resources, one reason that much of its electricity industry relies on nuclear power. It is the world’s third largest user of nuclear power.

Japan is the world’s third larger oil consumer, and it does produce some oil domestically. However, it also imports a lot of oil and natural gas, the later in the form of liquified natural gas, or LNG. Almost half of its energy came from imported oil in 2009, and just 16 percent of Japanese energy came from a domestic source.

Japan also invests heavily in foreign oil, including in the United Arab Emirates, the Congo, Algeria, Russia, Australia, Papua New Guinea, Brazil, Canada, the United Kingdom, Vietnam, and Indonesia, to name a few.

As of June 2011, Japan is still recovering from a massive earthquake and tsunami that devastated its northeast coast on March 11, 2011, forcing the shutdown of several nuclear reactors as well as damaging refineries, oil and gas generators, and electricity transmission infrastructure.

Japan imports most of its oil from the Middle East: Saudi Arabia, Iran, Kuwait, the United Arab Emirates, and Qatar together supplied 77 percent of imports in 2009.

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The Connection Between Greenhouse Gases, Climate Change & Global Warming



Climate change is the shift in long-term, global weather patterns due to human action; it’s not exclusive to warming or cooling.

Climate change includes any change resulting from different factors, like deforestation or an increase in greenhouse gases. Global warming is one type of climate change, and it refers to the increasing temperature of the surface of Earth. According to NASA, the term global warming gained popular use after geochemist Wallace Broecker published a 1975 paper titled Climatic Change: Are We on the Brink of a Pronounced Global Warming?

Since 1880, the average surface temperature of the Earth has increased by roughly 0.9 degrees Fahrenheit, but the rate it’s increasing is faster than that, depending on which region you live in. If you’re closer to the equator, temperatures are increasing more slowly. The fastest increase in temperatures in the United States is in Alaska, where average temperatures have been increases by more than 3 degrees Fahrenheit per century. For a graph of average global temperatures by year, see the NASA website here.



Greenhouse gases are those thought to contribute to the greenhouse effect, an overall warming of the Earth as atmospheric gases trap electromagnetic radiation from the sun that would otherwise have been reflected back out into space.

Noteworthy greenhouse gases are methane, nitrous oxide, carbon dioxide, hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). These gases are thought to affect the climate directly and indirectly, even though they constitute only a small fraction of the blanket of gases that make up the atmosphere.

Currently, the composition of the atmosphere is mostly nitrogen and oxygen, with just 0.033 percent carbon dioxide and all other gases accounting for even less.



According to 2010 models cited by NASA, 20 percent of the greenhouse effect is attributed directly to carbon dioxide and 5 percent to all other greenhouse gases. The remaining 75 percent of the greenhouse effect is thought to be due to water vapor and clouds, which are naturally-occurring. However, even though carbon dioxide and the other greenhouse gases are such a small percentage of the total gas in the atmosphere, they affect when, where and how clouds form, so greenhouse gases have some relevance when it comes to 100 percent of the greenhouse effect. Carbon dioxide is thought to modulate the overall climate, like a atmospheric thermostat.

Some greenhouse gases are produced in natural processes, like forest fires, animal manure and respiration, or volcanic eruptions. However, the majority of new greenhouse gases are produced from industrial processes and energy production.

The four largest human sources of U.S. greenhouse gases in 2009 were energy, non-fuel use of fossil fuels, natural gas production, and cement manufacture, in descending order. Non-fuel, greenhouse gas-producing applications of fuels include industrial production like asphalt, lubricants, waxes and other . Emissions related to cement manufacture happen when limestone (calcium carbonate) is reacted with silica to make clinker, the lumps ground to make cement. ( Emissions of Greenhouse Gases in the United States 2009: Independent Statistics & Analysis.)

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Physics and How Machines Work

Machines are so complicated these days it’s difficult to quickly explain how they work. Nonetheless, today’s machines were built using the basic principles of physics that we began harnessing hundreds of years ago.


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Water Depends on Energy, Or Is It The Other Way Around?

The United States took more than 400 billion gallons of water out of the ground, lakes, rivers, and reservoirs daily in 2005.  (more…)

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Basics of Electricity and Circuits: How Energy Moves Through the Home


The first major use of electricity began in 1879, when Thomas Edison began installing incandescent lighting in notable locations like Wall Street in New York City. Edison wasn’t alone in his pursuit of electricity development, but he was the first to install integrated systems in conspicuous places.

At that time, Americans used various other light sources, like oil lamps, candles, and fires. A candle gives off only around a single watt’s worth of light. Calcium (or lime) lights could provide a lot of light, but it was a harsh light and reserved for conditions like the theater, hence the term in the limelight.

Most lighting was very poor – and often dangerous – in comparison to fluorescent bulbs, and electricity became popular quite quickly. By the turn of the century, other electric devices began to become available, and by the 1920s, Americans could purchase electric refrigerators, dishwashers, and washing machines.

The first electrical systems depended on extremely local power plants, within a few blocks, or even within the building. As time passed, electricity development became a regional responsibility, and today, the United States is split into many different systems of electricity distribution, including both regulated municipalities and for-profit utilities.



Electricity isn’t merely the existence of electrons but the flow, and it is their flow that provides power. It’s a little bit like gravity and the flow of water downhill. Water will move spontaneously downhill because of gravity. Electrons (like other charged particles) move spontaneously when they are in electric fields. An electric field is generated when there’s a difference in electric potential – called a voltage – just like a hill exists when there’s a difference in altitude.

Electricity is the flow of electrons, which themselves are small charged particles associated with atoms. Under neutral conditions, electrons stay with the atom or group of atoms that make up a compound. However, one electron is indistinguishable from another and can move from one atom to an adjacent one if the atoms make up a conducting material, like various metals.

Voltage can be thought of as the height of the hill. The bigger the voltage, the more electrons want to move, and the more power can be delivered.

Cataract Falls, Mount Tamalpais, California

Electrons moving can be diverted to do work, sort of in the same way that water traveling downhill can be diverted to run a mill or turbine.

The water’s kinetic energy is lost as it is used up in the turbine. Likewise, the electrons’ kinetic energy is lost when they are put to work in a device. The electrons don’t get destroyed in the process of losing energy, just as the water wouldn’t be destroyed.



When you plug in something like a light, electrons flow from the plug, through the light, and back out through the plug. However, it’s not that simple, since we use what’s called alternating current, or AC, which means that the electrons flow one direction and then reverse direction. Alternating current makes it easy to change from a high voltage to a lower voltage. This change is made through a transformer.



Today, inside the home, electricity powers computers, televisions, telephones, lights, refrigerators, heaters, air conditioning, healthcare-related devices, video games, rechargeable toys, stereos, alarm systems, garage doors, ovens, stovetops, dishwashers, clothes washers, routers, can openers, DVD players, DVRs, and countless rechargeable devices like phones and electronic tablets.

Computers, televisions, and handheld electronic devices have become increasingly popular, while refrigeration, heating, and cooling have become more efficient. These recent trends in home electricity use have shifted the greater part of home energy needs from climate control to electronics.



Today, most households have more than two televisions, with 88 percent of homes have two or more televisions in 2009. The average household had 2.5 televisions. In the same year, 79 percent had DVD players, 43 percent had DVRs, and 86 percent of households had one or more computers. Nielson reported in May, 2011 that for the first time in 20 years, television ownership is slightly down, perhaps in part because computers may be replacing the use of televisions, DVDs, VCRs, and video games.


More about home energy in the energy efficiency section.

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Petroleum, Natural Gas, and Coal

The world depends on fossil fuels for its energy, and the United States is no exception. The vast majority of U.S. energy — more than 80 percent in 2009 — comes from burning fossil fuels. (more…)

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Energy Efficiency, Principles of Consumption, and Conservation

A blower-door test.

Transportation efficiency
Calculating home energy
Lighting efficiency
Heating and Cooling



When trying to lower your energy use, a good place to start is getting a picture of the many ways you use energy now.




An average American uses more than four times as much energy per year than the global average, 308 million British thermal units (Btu) annually, compared to 73 million Btu per person per year globally,according to recent U.S. government estimates. That guess doesn’t account for foreigners’ use of gathered fuels like wood or manure. However, it also doesn’t include the foreign energy used to source, assemble, and ship an endless profusion of products to the United States from other countries, like China.

The most straightforward uses that you can measure and control are probably in the home and through transportation. Every year, the average car in the United States is driven 12,300 miles and consumes about 67.8 million Btu worth of fuel. On average, Americans use more energy in homes than for transport.  The average household uses less (around 41 million Btu worth of electricity). However, to use electricity at home, we have to generate an additional 90 million Btu of primary energy at the power plant, according to the U.S. Energy Information Administration. What is a Btu?



Untangling the individual’s footprint comes with unrelenting complexities. Perhaps you live in an apartment in a big city and commute to work on the train, plug in your phone and computer at work, eat out every day, shower at a gym, and only come home to sleep. Maybe you travel for work, and your employer pays the expenses. You may pay almost nothing for energy directly. Yet, you are participating in energy use through your work, transportation, food, clothes, water, air travel, and electronic devices.

It’s also difficult to calculate how much energy is used up in buying new things. If you replace your car every two years, or you have a large home that you’re constantly remodeling, chances are your true energy footprint is much larger than you will be able to calculate.

The good news is you can calculate some aspects of your energy use and reduce it. And even if you plug in at work, it’s quite possible to make a decent ballpark estimate of how much energy that takes, too.



As a driving culture with access to cheap fuels — relative to our incomes — Americans use a lot of energy getting around. Transportation of goods and people accounted for almost a third of greenhouse gas emissions in 2009, according to the U.S. Energy Information Administration.

Reducing energy use in transportation is guaranteed by replacing car, truck, or motorcycle trips with biking or walking. For a normal healthy adult, walking a mile or two daily should be well within reach. Biking is a faster option, but it’s often considered a child’s transportation method in the United States. In countries like the Netherlands, it’s ordinary to see anyone on a bike, from babies in handlebar seats to well-groomed professionals.

Nonetheless, social customs, transportation infrastructure, suburban development, weather, and promotion of driving over other forms of transportation make it inconvenient and sometimes impossible to change Americans’ driving habits, at least without changing jobs or moving to a new city. A 2005 ABC News/Time magazine/Washington Post poll found that only 4 percent of 1,203 Americans used public transportation to get to work.

Even if driving is a must, driving efficiency can be improved. More efficient vehicles are available, like hybrids and some electric vehicles. Fuel economy can be improved by better car design and better driving. There’s also car-sharing and carpooling.

Analyzing, grouping, and prioritizing destinations can cut down on unnecessary trips. Yes, getting to work is mandatory perhaps, but a whopping 85 percent of car trips are for shopping, errands, and social or recreational reasons, according to a 2001-2002 government survey.

Other alternatives include public transit, ridesharing, and smaller transportation modes like skateboards, scooters, Segways and even electric bikes.

In China, the low-speed electric bicycle is extremely popular and far more efficient than driving or even taking the bus. It’s a regular pedal bike with a rechargeable battery that boosts the pedaler’s power but doesn’t travel faster than about 12.4 miles per hour. Somewhat heavier than standard bikes, electric bikes can still be pedaled without power on the flat or downhill, and the battery can help the rider stay sweat-free and comfortable on the uphill climb.



Estimating home energy use is getting easier now that utilities have installed smart meters that display electricity demand moment-to-moment. Depending on the utility that supplies your power, if you have a smart meter, you may already be able to log in online and track your hour-by-hour power use on any particular day, compare weekdays to weekends, or see if the house-sitter blasted the air conditioning. You can see how much electricity your home draws right now, and you can turn on and off appliances to see how each one contributes.

If you don’t have a smart meter, to calculate the energy that individual items in your home use, you need to look up how many watts each device — televisions, refrigerators, computers, routers, lights, electric air and water heaters — uses. That nameplate wattage is usually printed on the device.

Some sample nameplate wattages (watts):

Clock radio: 10
Coffeemaker: 10
Dishwasher: 1200-2400
Ceiling fan: 65-175
Space heater: 750-1500
Computer: 200-300 (awake), 20-60 asleep
Laptop: 50
Refrigerator: 725

Weekly energy per device = wattage x hours it’s “ON” per week

For devices that cycle on and off, like refrigerators and air conditioners, you’ll divide the resulting number by three.

You’ll also want to examine how much natural gas, propane, or other fuels you use for heating and cooling space, heating water, and cooking. While electric devices tend to be more efficient than gas-powered devices in your home, electric devices actually tend to use more energy overall because of loss of efficiency when the electricity was generated and transmitted to your home.

If you’re in the market for replacing you refrigerator or other appliance, and want to find out more about efficient options, a good resource for information is the Energy Star program.

Another detailed resource for tracking your energy-related emissions of greenhouse gas is the Home Energy Saver, built by the U.S. Department of Energy and Lawrence Berkeley Laboratory.

Know that devices don’t precisely use what their nameplate wattage says. Various factors affect how much energy something uses. For example, using the maximum brightness setting on a laptop computer will require more energy. Air conditioners will require much more energy to operate in very hot weather not only because it’s hotter outside but because the refrigerant becomes less efficient as it gets warmer, particularly if the refrigerant gets into the high nineties Fahrenheit. See below for more about heating and cooling.



You can improve your efficiency by replacing appliances and redoing construction, but you can also conserve energy by using less demanding settings, adjusting the thermostat, and turning items like computers and televisions off when they’re unused.



Unlike the days of candles and whale oil lamps, today we have many electrical lighting options. Our most popular, the standard 100 watt bulb, is being phased out, in part due to Clean Energy Act signed into law by President George W. Bush in 2007.  The maximum wattage incandescent bulb allowed will be 29 watts by 2014, down 70 percent from pre-2011 levels.

Instead, that type of bulb will be replaced by lower wattage incandescent bulbs, as well as compact fluorescent bulbs and even light-emitting diodes.

We can save lighting energy by

1. Turning off unused lights

2. Changing the type of light bulbs we use (see chart)

3. Changing the lighting plan, including adding natural light in the form of windows and skylights and solar tubes.

For more information about design, see the Energy Savers website.

Light can be measured in lumens. A 100 watt incandescent light bulb gives off around 1750 lumens.

The standard light bulb has a tungsten filament that exhibits incandescence when electric current travels through it. The filament burns out over time. The bulb keeps the filament in a special gas atmosphere like argon, instead of being exposed to regular air. Tungsten halogen bulbs operate somewhat similarly, with an incandescent filament, but the bulb contains halogen gas, which helps keep the filament from burning out as quickly.

Compact fluorescent bulbs, the sometimes spiral-looking bulbs, fluoresce instead of incandesce. Electric current travels through argon gas and a small amount of mercury vapor, which emit ultraviolet light. That light, in turn, excites a phosphor (fluorescent) coating on the inside of the bulb, which then emits visible light. So called CFLs are far more efficient and have much longer lifetimes. They do, however, contain a small amount of toxic mercury vapor and shouldn’t be thrown into the trash.

LEDs are also much more efficient than incandescent bulbs and don’t emit mercury if they’re broken. This technology is  sometimes called Solid State — even though the type of physics that the name is based upon has now changed to Condensed Matter. Extremely long-lived and very energy efficient, LED’s use around 20 percent of the energy of an incandescent for the same amount of light. However, they are far more expensive than similar fluorescent or incandescent options. For more about how LEDs work, go here.



Heating and cooling take a lot of energy. Replacing heaters, refrigerators, and single-paned windows costs money. Ripping out walls to add insulation is scary and can become a huge project.

However, today, a wide array of tools and professionals are available to assess the efficiency of heating and cooling and put it into perspective with cost. Home efficiency experts can use infrared detectors to track where heat is lost, and they can use blower door tests to check how quickly air is being exchanged with the outdoors through holes and leaky ducts.

Blower door tests change the air pressure inside a building relative to the outside to measure how quickly the air pressure returns to normal. If you walks through a pressurized house during the test, you can also track where air is leaking.

Even without a professional, you can reassess your home energy use. For tips on do-it-yourself home energy assessment, try the U.S. Department of Energy’s Energy Savers website.



1. Repairing leaky ducts, an often neglected source of heat loss! Ducts are much easier to access than replacing insulation, and they often have holes and cracks, making them a major  source of cold air infiltration, and also indoor air pollution.  Leaks suck in cold, dirty crawl space air including asbestos, dirt, and volatile chemicals (paint thinners, pesticides) that we stow or spray under the house. For more about indoor air quality see the Environmental Protection Agency’s website here.

2. Improve insulation and weather stripping, and seal up cracks. Use curtains or blinds to trap heat in during the winter and block sun out during the summer.

3. Replace air conditioners and heaters with more efficient models.

4. If you live in a dry climate, open windows to vent your home in the evenings, keep windows closed and A/C on during the morning before its the hottest hour of the day. Resist cranking the A/C up during the hottest hours of the day when the coolant fluid is the least efficient.

5. Replace windows and doors with better rated ones. For more about how windows are rated see the National Fenestration Rating Council.



The invention of new electricity-dependent devices outstrips the speed that we are making our homes more efficient. Today, heating, refrigerators, and air conditioners are using less energy, but televisions, computers, and an ever-expanding selection of other electronics are demanding more. For more about electricity in the home see the Basics of Electricity and how energy moves through the home.



A British thermal unit – almost always written Btu or BTU – is a measurement of thermal energy.  The scientific community usually uses the more manageable unit of the joule, which is a metric measurement of energy.  (A Btu is roughly 1,000 joules) A Btu is the English unit.

Fuels are often measured in Btu to show how much potential they have to heat water into steam or provide energy in other ways, like to engines. Steam turbines produce most of the electricity in the United States.


For more about the Smart Grid go to the Power Grid Technology section.

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Total U.S. Electric Output Per Week

This week (April 1 – April 7, 2012): 69,338 Gigawatt-hours
Change from this week last year: down 1.5%
This year (total of previous 52 weeks): 4,049,476 Gigawatt-hours


A Terawatt (1,000 Gigawatts) measures how much electricity is used at any single moment.
A Terawatt-hour (TWh) measures how much electricity was used over time.

Total U.S. Electric Output by Week



Weekly Electric Output is compiled from data collected through an online web data entry page from most of the country’s major, investor-owned utilities, municipalities, and Federal power agencies, accounting for roughly 75-80% of total electricity output. A multiplier is used to account for the other 3,000 small utilities that cannot be surveyed weekly.

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